1. Field of the Invention
The present invention relates to a thin film magnetoresistive (MR) head with improved resolution, and more particularly to a thin film MR head which includes a small gap with electrically conducting shields for transmitting sense current to a magnetoresistive element.
2. Discussion of the Related Art
In the electromagnetic recording arts, thin film flux sensing heads are desirable because of their high areal density capability. They are also easy to manufacture. With various thin film manufacturing techniques, they can be fabricated in batches on a substrate and then cut into individual units. A head employs a magnetoresistive element which changes resistance in response to magnetic flux density from a rotating magnetic disk or a moving magnetic tape. A sensing current, which is passed through the magnetoresistive element, provides variation in voltage proportional to the change in resistance of the magnetoresistive element. The linear response of the magnetoresistive element is based on how well the resistance change of the magnetoresistive element follows the change in flux density sensed from the magnetic medium. In a disk or tape drive, a differential preamplifier is connected to the magnetoresistive element for processing the output signals from the read head.
The magnetoresistive element is a thin film layer which has its thin film faces bounded by top and bottom surfaces and side surfaces. The bottom surface, which is elongated, forms a part of an air bearing surface which flies above the plane of a magnetic disk, for example, when the disk is rotated. The magnetoresistive element is sandwiched between a pair of gap (insulation) layers which in turn are sandwiched between a pair of shield layers. The distance between the shield layers is called the gap. The smaller the gap, the greater the resolution of the MR head. A magnetic field is applied along a "hard" axis of the magnetoresistive element to improve its linear response and a magnetic field is applied along an "easy" axis of the magnetoresistive material to improve its stability (reduction of Barkhausen noise).
In order to provide a small gap, it is desirable to keep the gap layers adjacent the magnetoresistive element as thin as possible. However, in the prior art, the gap layers had to be made thick enough to avoid electrical shorting caused by pinholes which are an artifact of the manufacturing process. Pinholes allow electrical shorting from the lead layers, which form the leads of an MR head, to the shield layers via the gap layers. Such shorting is commonly referred to as "lead-to-shield shorting". The chance of shorting can take place anywhere along the full length of either lead layer. Any shorts between the lead layers and the shield layers via the gap layers destroy the impedance balance at the two terminals to the differential preamplifier. This imbalance destroys the common mode rejection of electrical noise capacitively coupled to the lead layers from the slider body. Lead-to-shield shorting seriously reduces performance of the MR heads and reduces head yield in the manufacturing process.